在android中使用OpenGL ES需要三个步骤:
1. 创建GLSurfaceView组件,使用Activity来显示GLSurfaceView组建。
2. 为GLSurfaceView组建创建GLSurfaceView.Renderer实例,实现GLSurfaceView.Renderer类时需要实现该接口里的三个方法:
abstract void onDrawFrame(GL10 gl):Called to draw the current frame.
abstract void onSurfaceChanged(GL10 gl, int width, int height):Called when the surface changed size.
abstract void onSurfaceCreated(GL10 gl, EGLConfig config):Called when the surface is created or recreated.
3. 调用GLSurfaceView组建的setRenderer (GLSurfaceView.Renderer renderer) 方法指定Renderer对象,该对象将会完成GLSurfaceView里3D图形的绘制。
然后来看一个Demo,首先是主Activity:
package com.example.androidgldemo;import android.opengl.GLSurfaceView;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;public class AndroidGLDemo extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);GLSurfaceView glView = new GLSurfaceView(this);AndroidGLDemoRenderer renderer = new AndroidGLDemoRenderer();glView.setRenderer(renderer);setContentView(glView);}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.activity_main, menu);return true;}
}
然后是Renderer的实现:
package com.example.androidgldemo;import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;import android.opengl.GLSurfaceView.Renderer;public class AndroidGLDemoRenderer implements Renderer {float[] mTriangleData = new float[] {0.1f, 0.6f, 0.0f,-0.3f, 0.0f, 0.0f,0.3f, 0.1f, 0.0f};int[] mTriangleColor = new int[] {65535, 0, 0, 0, 0, 65535, 0, 0,0, 0, 65535, 0,};float[] mRectData = new float[] {0.4f, 0.4f, 0.0f,0.4f, -0.4f, 0.0f,-0.4f, 0.4f, 0.0f, -0.4f, -0.4f, 0.0f};int[] mRectColor = new int[] {0, 65535, 0, 0, 0, 0, 65535, 0, 65535, 0, 0, 0,65535, 65535, 0, 0,};FloatBuffer mTriangleDataBuffer;IntBuffer mTriangleColorBuffer;FloatBuffer mRectDataBuffer;IntBuffer mRectColorBuffer;public AndroidGLDemoRenderer() {mTriangleDataBuffer= bufferUtil(mTriangleData);mTriangleColorBuffer = bufferUtil(mTriangleColor);mRectDataBuffer = bufferUtil(mRectData);mRectColorBuffer = bufferUtil(mRectColor);}@Overridepublic void onDrawFrame(GL10 gl) {gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);gl.glEnableClientState(GL10.GL_COLOR_ARRAY);gl.glMatrixMode(GL10.GL_MODELVIEW);gl.glLoadIdentity();gl.glTranslatef(-0.6f, 0.0f, -1.5f);gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mTriangleDataBuffer);gl.glColorPointer(4, GL10.GL_FIXED, 0, mTriangleColorBuffer);gl.glDrawArrays(GL10.GL_TRIANGLES, 0, 3);gl.glLoadIdentity();gl.glTranslatef(0.6f, 0.8f, -1.5f);gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mRectDataBuffer);gl.glColorPointer(4, GL10.GL_FIXED, 0, mRectColorBuffer);gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);gl.glFinish();gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);}@Overridepublic void onSurfaceChanged(GL10 gl, int width, int height) {gl.glViewport(0, 0, width, height);gl.glMatrixMode(GL10.GL_PROJECTION);gl.glLoadIdentity();float ratio = (float) width / height;gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10);}@Overridepublic void onSurfaceCreated(GL10 gl, EGLConfig config) {gl.glDisable(GL10.GL_DITHER);gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST);gl.glClearColor(0, 0, 0, 0);gl.glShadeModel(GL10.GL_SMOOTH);gl.glEnable(GL10.GL_DEPTH_TEST);gl.glDepthFunc(GL10.GL_LEQUAL);}public IntBuffer bufferUtil(int []arr){ IntBuffer buffer;ByteBuffer qbb = ByteBuffer.allocateDirect(arr.length * 4);qbb.order(ByteOrder.nativeOrder());buffer = qbb.asIntBuffer();buffer.put(arr);buffer.position(0);return buffer;}public FloatBuffer bufferUtil(float []arr){ FloatBuffer buffer;ByteBuffer qbb = ByteBuffer.allocateDirect(arr.length * 4);qbb.order(ByteOrder.nativeOrder());buffer = qbb.asFloatBuffer();buffer.put(arr);buffer.position(0);return buffer;}
}
注意构造函数中那些Buffer的创建方式。在这个地方,不能直接使用FloatBuffer/IntBuffer 的wrap() method。直接用这个method创建出来的buffer会导致JE:
02-26 23:12:08.945: E/OpenGLES(2750): Application com.example.androidgldemo (SDK target 17) called a GL11 Pointer method with an indirect Buffer.
02-26 23:12:08.968: W/dalvikvm(2750): threadid=11: thread exiting with uncaught exception (group=0x40d57930)
02-26 23:12:08.984: E/AndroidRuntime(2750): FATAL EXCEPTION: GLThread 16938
02-26 23:12:08.984: E/AndroidRuntime(2750): java.lang.IllegalArgumentException: Must use a native order direct Buffer
02-26 23:12:08.984: E/AndroidRuntime(2750): at com.google.android.gles_jni.GLImpl.glVertexPointerBounds(Native Method)
02-26 23:12:08.984: E/AndroidRuntime(2750): at com.google.android.gles_jni.GLImpl.glVertexPointer(GLImpl.java:1122)
02-26 23:12:08.984: E/AndroidRuntime(2750): at com.example.androidgldemo.AndroidGLDemoRenderer.onDrawFrame(AndroidGLDemoRenderer.java:63)
02-26 23:12:08.984: E/AndroidRuntime(2750): at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1516)
02-26 23:12:08.984: E/AndroidRuntime(2750): at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)